1. Field of Invention
The present invention relates to a wrench for providing two operative modes for driving a fastener.
2. Related Prior Art
A selective one-way wrench includes a handle, a head formed on the handle, a mandrel, a transmitting unit and a direction-selecting unit operable for selecting one of two directions in which the head drives the mandrel through the transmitting unit.
The wrench can be used together with a socket to slack or tighten a fastener. The mandrel is inserted in an end of the socket while the fastener is inserted in an opposite end of the socket.
To slack the fastener, the wrench is used to exert a large torque on the fastener initially. Once the fastener is slacked, it would be faster to drive the fastener with a bare hand than with the wrench.
To tighten the fastener, it would be faster to drive the fastener with a bare hand than with the wrench initially. At a final stage, the wrench is used to exert a large torque on the fastener.
There are wrenches each including a handle, a head formed on the handle, a mandrel, a transmitting unit, a direction-selecting unit operable for selecting one of two directions in which the head drives the mandrel through the transmitting unit and a shaft connected to the transmitting unit. At an initial stage of a slacking operation or a final stage of a tightening operation, the handle is operated to drive the mandrel through the transmitting unit. For the rest of the slacking or tightening operation, the shaft is operated to drive the mandrel through the transmitting unit. Such wrenches can be found in EP 0486710, U.S. Pat. No. 454,567, U.S. Pat. No. 5,105,688, U.S. Pat. No. 6,070,499, WO 8803999, WO 9207692 and Taiwanese Patent Publication No. 494828 for example. In each of these wrenches, the head is secured to the handle and this could be inconvenient when it is used in limited space.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.